This invention relates to an air conditioning system of the so-called reheat air-mix type for use in automotive vehicles, and more particularly to a discharge air temperature control device for such systems.
In a conventional air conditioning system of the so-called reheat air-mix type for use in automotive vehicles, a heater core is arranged at a location downstream of an evaporator core, with an air-mix damper located in the vicinity of the heater core. The angular position of the air-mix damper determines the mixture ratio of cooled air supplied from the evaporator core through a by-pass passage and heated air supplied from the heater core which mixture ratio in turn determines the discharge air temperature. With this arrangement, control of the discharge air temperature is feasible only by adjustment of the angular position of the air-mix damper so as to obtain a desired passenger compartment temperature. Further, part of air dehumidified by the evaporator core is reheated by the heater core, which permits dehumidifying-heating operation (Dry Mode Operation) at any desired time.
However, according to the conventional air conditioning system of the reheat air-mix type, adjustment of the capacity or rate of operation of the evaporator is not possible during operation, as distinct from the so-called combined heater and cooling system. That is, the evaporator operates all the time during operation of the air conditioning system. Therefore, even when dehumidifying operation is not required, the compressor is driven so that the evaporator operates at maximum capacity, which results in consumption of a large amount of energy by the air conditioning system.